1. TECHNICAL FIELD
The invention relates to end caps for air springs, and more particularly to the clamping means adapted to affix a resilient elastomeric sleeve member to a relatively rigid cap or piston member of an air spring. Specifically, the invention relates to a clamp assembly for an air spring employing an annular recess in the end cap which provides a hidden cavity for an uncompressed end of the sleeve member which extends beyond the compressed sealing area of the sleeve.
2. BACKGROUND INFORMATION
Pneumatic springs commonly referred to as air springs, have been used for motor vehicles for a number of years to provide cushioning between moveable parts of the vehicle, primarily to absorb shock loads impressed on the vehicle axles by the wheels striking an object in the road or falling into a depression. The air spring usually consists of a flexible rubber sleeve or bellows containing a supply of compressed fluid and has one or more pistons located within the flexible sleeve. The piston causes compression and expansion of the fluid within the sleeve as the sleeve compresses and expands as the vehicle experiences the road shock. The spring sleeve is formed of a flexible elastomeric material which permits the piston to move axially with respect to another piston or end cap secured within the ends of the sleeve.
The ends of the sleeves are sealingly connected to the piston and/or opposite end cap and are always one of the important and major aspects in producing an efficient and maintenance free air spring. One problem with certain air springs is that the exposed cut edge at the end of the elastomeric sleeve of the air spring will engage the sleeve body as it rolls along the piston or end cap in excessive stroke conditions causing excess wear to the flexible sleeve. Another problem with existing air springs, and in particular, the clamp ring therefore, is that the clamp ring will move in its clamped position under dynamic air spring conditions causing movement of the clamped elastomeric material therebetween tending to loosen the sealing engagement and deteriorating the clamp integrity and causing ultimate air spring leakage and failure. This ring movement is especially critical during the jounce or collapsing stroke.
Another problem with existing air springs and the clamping of the elastomeric sleeve ends to the piston member and/or end cap is to secure a sufficiently tight seal to be able to withstand high fluid pressures contained in the fluid chamber without premature leakage or bursting even upon experiencing severe air spring movement and being exposed to the harsh environments on the undercarriage of a vehicle.
Some examples of air springs and band sealing devices are shown in the following patents described below:
U.S. Pat. No. 3,788,628 discloses a pneumatic spring-type system including a structure for anchoring the inner ends of a flexible rolling sleeve. The sleeve is positioned between surfaces characterized by having a saw-toothed shape with a circumferential groove and rib on an inner circumferential surface and two ribs on an outer circumferential surface. The opposite sides of the grooves converge at predefined angles with predetermined and matching radii of curvatures, the combination of which provides a gripping action to hold the flexible sleeve firmly in place by means of the saw-tooth design in cooperation with the matching recess of the ring and sleeve flange.
U.S. Pat. No. 3,870,286 relates to a fluid spring wherein the ends of the rolling sleeve are secured by annular clamping rings which engage against the internal surface of the sleeve. The clamping ring secures the rolling sleeve to the working cylinder with the clamping ring containing an annular groove type deformation by which the rolling sleeve is held in place by virtue of this interacting groove-shaped design in combination with the clamping force exerted by the ring.
U.S. Patent No. 4, 489,474 relates to means for connecting a tubular flexible member to a piston which includes a recess near the piston end which is secured to a flexible member. The flexible member is wrapped over and around a ring-shaped fitting which secures the flexible member to the piston. The piston comprises a circumferentially extending recess adjacent to its end with the flexible sleeve being positioned and substantially filling the recess of the piston. The ring-shaped fitting is a conventional swaged ring and the end portion of the flexible member is trimmed from the portion extending from the piston ring with the flexible member substantially filing the recess of the shoulder of the piston. The piston employs a serrated edge to assist in griping of the flexible member.
U.S. Pat. No. 4,457,692 discloses an assembly for sealing two members, one of which has a cylindrical surface which supports the seal, wherein a sealing lip is provided to bear against the second member. A cylindrical surface supports the seal which comprises a hollow-cylindrical body having a lip which extends outwardly from the body with an elastomeric band circling the body to hold it firmly in place. The cylindrical surface contains a recess which extends circumferentially around the surface and receives a matching projecting element of the seal which extends from the inside diameter of the cylindrical body.
U.S. Pat. No. 4,629,170 relates to a pneumatic spring with a pair of chambers formed by a pair of membranes that are sealingly attached to an axially spaced apart retainer and piston wherein the axial end of the membrane is compressed between a serrated surface of a solid member and a retaining ring wherein the ring may be swaged, fitted or otherwise tightened to produce radial compression against the axial ends of the flexible membranes.
British Pat. No. 199,789 discloses a metal securing band which grips a diaphragm and forces it against a tapered end portion of a tubular member.
U.S. Pat. No. 4,718,650 shows an air spring in which the ends of the flexible sleeves are connected to the sealing surfaces of a pair of axially spaced pistons by swaged crimped clamping rings. The piston clamping surfaces are formed with serrations for assisting to retain the elastomeric material when forced therein by the clamping rings.
Other types of piston and end cap sealing arrangements for air springs are shown in pending patent application U.S. Ser. Nos. 62,984: filed June 17, 1987; 94,479, filed June 8, 1987; and U.S. Pat. No. 4,784,376 all of which have been assigned to the Assignee of the present invention.
Another known prior art air spring construction includes a radially extending shoulder formed on the piston member on which the clamping ring seats and sealingly clamps the cut end of the flexible sleeve against a plurality of uniformity raised ribs formed on the axially extending sealing surface of the piston member adjacent the annular shoulder. However, in such construction the clamp ring is not positively positioned on the annular shoulder, and is free to move in an upward axial direction upon the air spring experiencing severe jounce or extended positioning, and the entire end of the sleeve is in a compressed state.